Much research has shown that there is a deterioration in cognitive functioning in old age. The present research is concerned with expanding our knowledge of cognitive changes associated with aging by examining adult age differences in concept acquisition skills. Previous research in this area has suggested that the ability to acquire new concepts declines with age in adulthood. However, the tasks that have been used previously to study aging effects on concept acquisition may not be analogous to naturalistic concept formation situations. Preliminary studies have shown that adult age differences are minimal in situations more closely approximating everyday concept learning. For present purposes, it is hypothesized that there are two ways in which concept learning can occur, and the type of learning emphasized in a given situation will determine the extent to which age differences will occur. The first way concept learning can occur is through the memorization and use of information about specific items in a category, a process assumed to be dependent on age-related memory skills. The second way involves the abstraction of central tendency (or prototypical) information about a group of related stimuli, which is hypothesized to be an automatic process unaffected by aging. A conceptual framework is proposed for distinguishing between those situations in which age differences will and will not occur in a given task situation by taking into account the task requirements, the type of concept learning emphasized, and the abilities available to a given individual. The utility of this framework will be critically examined in a series of four experiments. It is the long-term aim of this research to identify those processes which do and do not decline with aging and to ultimately be able to predict under what conditions age decrements will be observed. Such information will be of great importance when considering the effects of aging on performance in a given job situation. It is hoped that such knowledge will also eventually facilitate the formulation of a comprehensive theory of adult cognitive development.